September 28, 2018 marked the day that a brand new drug named Libtayo (cemiplimab-rwlc) was released on the market. The drug is the first of its kind to be approved by the FDA for the treatment of advanced cutaneous squamous cell carcinoma (CSCC), the second most common form of skin cancer. While squamous cell carcinoma is generally treatable via surgical removal of the cancerous tissues, in a small percentage of people the cancer will progress to an advanced form and will no longer respond to traditional treatment. The development of Libtayo has addressed this issue.
Tumors cells of CSCC go undetected by the immune response by activating the Programmed-Death-1 (PD-1) pathway of activated T-cells. Activated T-cells play an important role in tumor suppressing immune response. The PD-1 pathway is usually activated by normal cells. Binding of a normal cell to the PD-1 receptor of an activated T-cell indicates that there are no tumor cells. When activated by normal cells the PD-1 pathway inhibits tumor suppressing immune response. Tumor cells have PD-1 ligands that binds to the activated T-cell and elicits the same response as normal cells. By this mechanism, tumor cells are undetected by the immune system and continue proliferating.
Libtyo is a “recombinant human IgG4 monoclonal antibody” that targets PD-1 receptors of activated T-cells (Lexicomp). Libtayo binds to the PD-1 receptor, thereby preventing the tumor cells’ PD-1 ligand from binding on to PD-1 receptor of activated T-cells. Therefore, the tumor cell is unable to activate the PD-1 Pathway. Activated T-cells continue their tumor suppressing immune response and start targeting the tumor cells. By this mechanism Libtayo prevents advancement of CSCC, and boosts the immune response against the existing tumor cells.
Although Libtayo does prove useful in treating advanced CSCC, its most common side effects include fatigue, rash, and diarrhea. Some less common side effects can be high blood sugar, organ problems (thyroid gland, kidney, liver, muscle problems), bad breath, thirst and hunger, and sometimes certain brain problems. Libtayo has a recommended dosage of 350 mg administered intravenously at 30 minutes intervals for 3 weeks until disease progression or unacceptable toxicity. The degree at which the drug is distributed into the body tissue is 5.2 L and this is excreted at 0.2 L per day, which makes the dosing recommendations make more sense – a large amount is distributed, but only a small amount of that is excreted per day.
In Conclusion, the approval of Libtayo is important to Pharmacists because they are the de facto frontline provider in the medical field, therefore understanding the knowledge behind the approval and formation of new drug will prove helpful for counseling patients. Additionally, with oral chemotherapy regimens, the patient will visit the pharmacist more often (for medication refills, supporting medications, augmentation from over-the-counter products, etc) than the oncologist or oncology nurse; therefore, it’s very important that the pharmacist is as knowledgeable about the drug as the nurse or physician.
